Many scientists believe the extinction was caused by an asteroid impact, while some think regional volcanism was to blame, and others suspect it was due to a combination of the two

Dinosaurs were killed off by a 'one-two punch': Deadly volcanic eruption AND an asteroid strike led to their extinction

One of the planet’s largest extinctions, which wiped out non-flying dinosaurs and most other species 66 million years ago, was caused by a “one-two punch” of volcanic eruptions and meteorite impacts, a new reconstruction of Antarctic Ocean temperatures suggests.

The research, which was published in the journal Nature Communications on Tuesday, is the latest intervention in an ongoing debate whether meteorite impacts or volcanoes brought about the extinction at the end of the Cretaceous Period.

“The place where we performed the study, Seymour Island, is a unique site for studying this period,” says Sierra V. Petersen, a postdoctoral fellow at the University of Michigan and one of the report’s authors. In most locations, the sediment cores that contain the fossil researchers use to study historical temperatures have been compressed to one or two metres, but on the island at the tip of the Antarctic peninsula, “that time interval is 40 meters.”

Those 40 metres may be less compressed than most samples, but a wealth of information is still packed into Seymour Island’s sediment cores: “The temperature record that we published lasts about 3.5 million years.”

According to that record, temperatures spiked after the eruption of India’s Deccan Traps volcanoes. “We think that change could have been caused by carbon dioxide emitted by the volcano,” which made it harder for heat to escape the atmosphere, Petersen says.

When meteorites did strike, about 150,000 years after the Deccan Traps eruptions, the sediment cores suggest that another temperature spike occurred. “The combined extinction in this last little breath of the Cretaceous Period can be linked to both the volcano and the meteorite through this climate change record,” Petersen says.

The extinction, she says, “was not very discriminatory.” In addition to non-flying dinosaurs, it wiped out most plant life and bivalve molluscs. “It was extremely catastrophic.”

During the period covered by the study, temperatures reached 10 or 11 degrees celsius in shallow water. Today, Petersen says air temperatures at Seymour Island “barely gets above freezing even in the warmest months. Those temperatures, however, were not unprecedented in the Antarctic, which was forested at the time.

“The maximum temperature that was reached had also been experienced by those organisms a million years before,” Petersen says. In this case, the difference was the speed at which temperatures rose. She continues: “The faster the climate changes the more stress that adds on organisms because they have to adapt more quickly.”

The faster the climate changes the more stress that adds on organisms because they have to adapt more quickly.
The paper, which was co-authored with Andrea Dutton and Kyger C. Lohmann, only contains temperature information from one location, which researchers are looking to relate to the rest of the world.

“Today the Arctic is warming at double the rate of the global temperature average,” Petersen says. “We think the same kind of amplification that is happening today may have happened in the Antarctic in the past.”

Researchers hope to use the advanced dating techniques employed at Seymour Island to investigate the global trends this new information hints at.

“We’re going to try to do similar studies in other locations,” Petersen says, “and continue to try to look at not only this climate in one place but the global picture of climate.”